Date of Award




Document Type

Master's Thesis

Degree Name

Master of Arts (MA)


Department of Psychology


Clinical Psychology

Content Description

1 online resource (vi, 60 pages) : illustrations (some color)

Dissertation/Thesis Chair

John P Forsyth

Committee Members

John P Forsyth, James F Boswell


acceptance and commitment therapy, cognitive defusion, implicit assessment, relational frame theory, Acceptance and commitment therapy, Adaptability (Psychology), Mindfulness-based cognitive therapy, Operant behavior

Subject Categories



Acceptance and commitment therapy (ACT) emphasizes the relationship people have with unwanted thoughts, emotions, and other private events. ACT utilizes cognitive defusion strategies to reduce the believability of unwanted, distressing thoughts so as to foster greater psychological flexibility. Though defusion is linked to several positive behavioral outcomes (e.g., improved pain tolerance), it remains unclear whether such effects are associated with the behavioral process of defusion itself, namely, behavior that is more sensitive to direct contingencies compared with behavior influenced by unhelpful verbal functions. To address this issue, the present study assessed the impact of a defusion intervention on behavior, as measured by the Implicit Relational Assessment Procedure (IRAP). Undergraduates high in spider fear (N = 65) were randomly assigned to one of two interventions targeting personally relevant phobic thoughts of spiders: a word repeating defusion intervention or a thought distraction intervention. A third inactive control condition (reading an article) was used to evaluate the relative impact of both interventions. Participants completed the IRAP and self-report rating scales of believability and distress of target thoughts pre- and post-intervention. Consistent with expectation, defusion produced significantly greater pre- to post-intervention reductions in IRAP effects and thought believability relative to comparison conditions, suggesting defused behavior under greater control of direct contingencies relative to verbal functions. Results are discussed in the context of assessing the behavioral processes at the core of ACT-based interventions.

Included in

Psychology Commons